1. Field of the Invention
This invention relates to decking systems in which the deck height can be adjusted and more particularly to such a system for use in supporting freight in a vehicle compartment and to improved method and apparatus for adjusting the deck height.
2. Description of the Prior Art
In vehicles employed for handling freight such as trucks, aircraft and railroad cars, it is often desirable to provide beams, decks, or shelves to support various cargo items. In order to facilitate loading and unloading of such cargo, it is desirable that such cargo support systems be versatile in their positioning and readily relocated from the cargo handling area to a stowage location if need be. In U.S. Pat. No. 5,338,137, inventor: Richard H. Jensen, issued Aug. 16, 1994 and assigned to Ancra International, LLC, the assignee of the present application, a decking system is described which employs paired beams for supporting a shelf or for directly supporting cargo containers. In this system, the height of the deck can be raised or lowered by means of latching members which engage apertures formed in opposing vertically support tracks.
In U.S. Pat. No. 6,074,143, inventors Francis J. Langston and Ward C. Burroughs, issued Jun. 13, 2000, assigned to Ancra International, LLC, there is described an improvement over this prior art decking system of U.S. Pat. No. 5,338,137 in that it provides dual latching fingers on lock keys that are pivotally mounted on guide shoes and the guide shoes can move upwardly and downwardly on the opposed tracks to thereby raise and lower the height of the decking system. The latching fingers engage a pair of apertures in the tracks, thus distributing the load and providing greater strength. A biasing spring provides a force to bias the lock keys towards the track and the latching fingers into engagement in the apertures. The lock keys are provided with tabs to allow manipulation of the latching fingers of the lock keys into and out of apertures in the tracks to provide for the height adjustment of the guide shoes on the track.
When not in use as shelf supports, the guide shoes are generally stored at or near the ceiling or roof of the freight container, such as a cargo vehicle, in which the decking system is used. When it is desired to move the guide shoes to a new height, the guide shoes must be moved downwardly on the track.
When the track, the guide shoes and the lock keys are relatively new and clean, manual manipulation force on the tabs on the lock keys to remove and hold the latching fingers out of engagement with the apertures in the track against the force of the biasing spring is easily done by a person's thumb or finger pressing on the tab to provide a minimum manual force exerted on the tab. Gravity then provides sufficient force on the guide shoes to allow the guide shoes to move downwardly to a desired height while the latching fingers are out of engagement with the apertures. The minimum manual force exerted by the person's thumb or finger on the tab is then removed and the latching fingers re-engage into the apertures of the track under the force of the biasing spring.
In some applications of the invention described in U.S. Pat. No. 6,074,143, it has been found that wear over extended time periods of use and/or in gritty or corrosive environments the guide shoes may not move freely on the tracks and/or the latching fingers may not easily be released from the apertures in the track by the minimum manual force exerted by a person's thumb or finger when it is desired to adjust the height of the guide shoes to thereby adjust the height of the shelving and gravity forces are not strong enough to move guide shoes downwardly to a desired height. In some prior art applications for these conditions, pry bars have been utilized to move the latching fingers out of engagement in the apertures in the track but gravity alone has not been sufficient to caus the guide shoes to move downwardly to a selected height.